Pneumatically-operated electric switch



P 6. s. M E YFARTH I PNEUMATICALLY OPERATED ELECTRIC SWITCH Filed Aug. 1, 1924 atented Ann 3%, i929.

UNITEE) STATES ZEZRLAND, ASSIGh -OB OF CHE-HALF 'iO QEEGN, OE GENEVA, SV .ZTZERLAND, .A.

?NEU1WATIOALLY-OPERATED ELECTRIC SWITCH.

Application filed August 1, 1924, Serial No. 729,659, and in Switzerland September 4, 1923.

The present invention relates to improvements in devices for mechanically controlling a group of pneumatically operated electric switches.

It is known to control a set of pneumatically operated el ctric switches by mechanically actuating the air valves. This control hitherto has not been applicable to motors more particularly on electrically driven vehicles because faulty or short-circuit-preducing switching was liable to occur in the main circuits, since no interlocking meainf were provided between the switch in its contact positions for the main c'rcuits and the mechanisn'i operating the pneumatic valves.

The present invention remedies this condition of things by providing means whereby the mechanism actuating the valves of the switches is mechanically 'nterlocked in accordance with the contac icsition oi the t 1 switches so that t e working or L not be faulty.

Two constructional examples of the device according to the present invention are dis. grammatically illustrated in the accompanying drawings in which Fig. l is a view oi one construction and Figs. 2, 3 and a illustrate some oi the elements of a second construction in various positions.

1e latter can- Fig. 1 shows a set of three singl switches 1, 2, 3 belonging to a vehicle control for single phase current. The contacts 16 thereof are on various points or the secondary winding of a step transformer {not shown). the motors being fed through the said contacts and through a choke coil (not shown). It is assumed that the switches l and 3 are connected to the same end of the choke coil, the switch 2 being connected to the other and thereof so that the switch 8 must first be closed when the switch 1 is open and conversely the switch 1 must first be closed when 3 is open, for the purpose of preventing short-circuits.

The contacts 16 operated by a rod 1? displaced in the circuit-closing direction by a piston 14 moving in compressed air cylinder 13 and in the circuit-opening direction by a spring 15.' The ingress and egress of air into and out or the cylinder 13 is controlled by two valves 11 and 12 mounted on a common stem fitted with a roller. T he rollers of all the stems 1O co-operate with the travelling nut member or runner 7 surrounding a suitably threaded spindle 6 rotated by hand with the aid of two sprockets and a chain 5. The shaft 21 of the driving sprocket is rotated by means or" the hand wheel 20 of the controller l through a friction clutch 22 and a spring clutch 23.

The travelling nut member 7 has an operating member 8 adapted to contact with the rollers of the stems 10, and two interlocking ni-mbers 9 cooperating with interlocking rods 19 one of which is titted to each switch 1, 2, 3. Tlhe rods 19 are actuated by the piston rods 1? through the medium of suitably pivoted levers 18. The accurate position of the travelling nut l" and therefore of the switches 1 2, may be read off an indicator device comprising the hand 2% moved by means of the threaded portion of the shaft 21.

inc construction just described works as in Fig. 1 the stems 10 of the valves closed v" ile the switch 3 is open. It now the travelli' g nut member is moved in the direction of the arrow, the rod 10 of the switch 1 comes out of contact with the operating member so that the said switch is opened. The interlocking rod 19 is raised owing to the contacts 16 moving apart from each other so that unobstructed passage is aiiorded to the left interlocking member 9. Should the contact 16 not be opened by the switch 1 for any ause, the interlocking rod 19 is not raised the left interlocking member 9 touches said red when the nut member 7 is operated in the direction of the arrow so that the said nut member cannot move further, this g place before the stem 10 of the switch 3 is engaged by the operating member 8. Un-

due sti on the drive due to the interspection of hand controls with those of hi h switching power and rapidity afforded by pneumatically-operated switches.

Cams may be used when, in contradistinction to the construction described, the sequence of switching operations is not uniform. Referring to the construction of Figs. 2, 3 and 4, the air valves 11 and 12 and their stem 10 are actuated by a cam 26 keyed to a shaft 25. An interlocking sector 27 is provided for interlocking the shaft 25 in case the contacts 16 or the switch are in the incorrect position. To this end, an interlocking pawl 29 operated by means of the piston rod 17, the lever 18 and the link 28, comes in contact with the said sector.

This construction works as follows: F 2 shows the roller of the stem 10 on the boss of the cam 26, the valve 11 being thus ope forthe inflow of compressed air into the cylinder 13 and the contacts 16 being closed. In Fig. 3 the cam has angular-1y moved in the direction of the arrow from the position of Fig. 2 so that the roller of the stem 10 is out of contact with the boss, and the outlet valve 12 is open. Assuming now that the contact 16 has remained closed, the interlocking sector is in engagement with the interlocking pawl 29 so that the shaft 25 cannot be iurther rotated. Referring to Fig. 4;, it is now as sumed that the contacts 16 are open; the in terlocking pawl 29 ail'ords unobstruct movement to the sector 27 in the direction oi the arrow so that the shaft can be further rotated. It will be clearly seen from the above description that the switches cannot be incorrectly worked wing to the interlockin means provided therefor.

The hand drive may of course be replaced by a servo-motor, for example an electric motor or by a pressure-operated driving ap" paratus.

I claim:

1. In an apparatus of the class described, a plurality of switches each having a Li and a movable contact, means for mechanically operating the movable contact of each individual switch to open the same and for pneumatically operating the movable contact of each switch individually to clos the same, a carriage having a surface tixed relatively thereto for controlling the means for the pneumatic operation of the said movable contacts of the said switches, whereby any one of the said switches may be automatically actuated and maintained in a closed position only after another switch has been opened, and means for operating the said carriage.

2. In an apparatus of the class described, a plurality of electric switches each having a fixed and a. movable contact, means for mechanically operating the movable contact of each switch individually to open the same and for pneumatically operating the movable contact oi each switch individually to close the same, a carriage provided with a surface fixed relatively thereto for actuating the pneumatic means for operating the movable contact of each switch, a stop device associated with the movable contact of each switch, the said single movable mechanical member also being prov'ded with a surface adapted to contact with the said stop device of the movable contact of each switch when the switch is closed whereby no one of the said switches can be closed until after another switch has been opened, and means for operating the said carriage.

3. In an apparatus oi' the class described, a plurality of switches each having a fixed and a movable contact, devices for individually operating the said switches each comprising a cylinder, a piston, a piston rod to which the movable contact of the corresponding switch is connected, a spring tor moving the piston in one diregtion to open the switch, and pneumatic devic for actuating the piston in the direction. to close the switch, a carhaving a sis'i ace i'ixed relatively thereand adapted to e age the said pneumatic i g a predetermined numfi iain a predetermined and nl er of s vitches in a closed osition only alter another switch has been opened, and means for operating the said carriage.

In an apparatus oi? the class described, a plurality ot switches each having a fixed a movable contact. devices tor individcylindcr, a piston, a piston rod to I he movable contact 0 the correspondg tclris connected, a spring for moving the piston in cue direction to open the switch, and pneumatic devices for actuating'the piston in the opposite direction to close the switch, a sing e n'iovable mechanical member lmving a surface fixed relatively thereto and adapted to engage the said pneumatic devices for operating a predetermined number thercor? to nn'iintsio a nedetermined and corresponding number of switches in a closed position, a stop device associated with the movable contact oi? each switch adapted to be encaged when the switch is closed by another surface on the said single movable mechanical member whereby the said switch must be opened to permit the stop device to be clear the said second snrtacc on the single movable mechanical member before the said member can be moved to close another switch, and means for operating the said single movable mechanical, member. In testin'iony whereof I. have a tlixed my signature.

(l OTTLIEB M E YFAR Tl I. 

